Some questions to be answered in the 1 second he points it at you:

+ How do you know your partner is behind you?

+ How do you know he won't take your gun after he uses the taser on you?

+ How do you know it was a taser?

+ Are you confident enough in those answers to miss your daughter's next birthday?

Have you seen the video? The cop drops his own taser and draws his firearm as the victim runs away. Why would he do that? Because he knows his taser is out of range, won't reach the victim.

So he knows his taser has the stopping power of a nerf gun at that point. The corollary is that he knows the taser in the hands of the victim is also out of range, also has the stopping power of a nerf gun. After this is known, because it is known, he drops his taser and draws his pistol, which does have the range.